This is a First-Person Puzzle game, but at the time of this writing, I haven't played Portal, so my review is going to be based on its own merits. With that out of the way, this makes its way from simple to complex, but does it gradually enough that you don't ever really get left behind, and there is no need for any real tutorial. There are cubes of several different colors, and each does something a bit differently. Most of their parameters are pretty easy to figure out, and they're introduced very well, so you actually are figuring things out. The actual puzzles are also often very thoughtful; they begin with simple objectives, like getting to the door, but later, you'll be sending balls through obstacle courses, mixing colors, and more. The actual puzzles take some effort to figure out, and you might have to experiment a little until you get it. My mind isn't wired for puzzle solving of this nature, but the game helped to develop that part of me, at least a little. There were only 2 puzzles that I really hated, and from what I've been reading, I'm not alone on at least one of them. It wasn't enough to ruin the experience, though; I'd still recommend this.
The visuals were very simple, but they did a good job not only creating an environment that was easy to understand, but also develop a bit of lore, even if you never learn much about it. The music and sound were decent; they did their job. There was a story, and while I didn't care all that much about it - I was in this for the puzzles - it did keep me guessing until the end, and most of my guesses were wrong, for whatever that's worth.